The present invention relates to inkjet printheads. In particular, it relates to a nozzle plate thereof formed with at least two positive photoresist layers that undergo a single removal of unwanted photoresist materials.
The art of inkjet printing is relatively well known. In general, an image is produced by emitting ink drops from a printhead at precise moments such that they impact a print medium at a desired location. The printhead is supported by a movable print carriage within a device, such as an inkjet printer, and is caused to reciprocate relative to an advancing print medium and emit ink drops at times pursuant to commands of a microprocessor or other controller. The timing of the ink drop emissions corresponds to a pattern of pixels of the image being printed. Other than printers, familiar devices incorporating inkjet technology include fax machines, all-in-ones, photo printers, and graphics plotters, to name a few.
A conventional thermal inkjet printhead includes access to a local or remote supply of color or mono ink, a heater chip, a nozzle or orifice plate attached or formed with the heater chip, and an input/output connector, such as a tape automated bond (TAB) circuit, for electrically connecting the heater chip to the printer during use. The heater chip, in turn, typically includes a plurality of thin film resistors or heater elements fabricated by deposition, masking and etching techniques on a substrate such as silicon.
To print or emit a single drop of ink, an individual heater is uniquely addressed with a predetermined amount of current to rapidly heat a small volume of ink. This causes the ink to vaporize in a local bubble chamber (between the heater and nozzle plate) and be ejected through the nozzle plate towards the print medium.
Typically, nozzle plates that attach to the heater chip, post-chip-formation, have certain economic and mechanical drawbacks relating to the alignment between the nozzle plate orifices and the heater elements. As is known, poor alignment causes product defects or ineffectiveness. On the other hand, nozzle plates concurrently formed with the heater chip often suffer deformations in ink flow features or nozzle orifice shapes upon subsequent chip processing steps. Again, product defects or ineffectiveness can result. In addition, concurrently formed nozzle plates often require multiple solvent dissolving/removal steps which add cost and complexity to the fabrication sequence.
Accordingly, a need exists in the nozzle plate art for economic and simple designs that overcome misalignment and malformation and require minimal processing steps.
The above-mentioned and other problems become solved by applying the principles and teachings associated with the hereinafter described inkjet printhead having a nozzle plate formed with at least two positive acting photoresist layers.
In one embodiment, the invention teaches a nozzle plate for a substrate made by initially forming a first reverse imageable positive photoresist layer on the substrate. In an area thereof adjacent an ink ejection element, the first layer is protected from energy rays while areas other than the protected area are subjected to such energy. The non-protected area is heated to cross-link it and make it substantially insoluble. Thereafter, energy rays expose the protected area to weaken its composition for later removal. A second reverse imageable positive resist layer gets formed on the first layer and, in a region directly above the ink ejection element, is exposed to energy rays. Subsequently, both the protected area of the first layer and the non-protected region of the second layer are removed in a single processing step by an alkaline solvent. This forms an ink flow feature, a bubble chamber and/or a nozzle orifice of the nozzle plate. Finally, the remaining portions of the first and second layers are blanket exposed to energy rays and heated to cure them in place.
In other aspects of the invention, the layers become formed by spin casting a solution or laminating a dry film of positive photoresist material directly on the substrate containing ink ejection elements. Exposure of the layers to energy rays, such as ultraviolet radiation, followed by heat, leads to cross-linking of the layers in specific patterns consistent with a pattern of a photomask.
Inkjet printers and inkjet printheads are also disclosed.
These and other embodiments, aspects, advantages, and features of the present invention will be set forth in the description which follows, and in part will become apparent to those of ordinary skill in the art by reference to the following description of the invention and referenced drawings or by practice of the invention. The aspects, advantages, and features of the invention are realized and attained by means of the instrumentalities, procedures, and combinations particularly pointed out in the appended claims.